This invention relates to a gear, such as a spiral bevel gear, formed with a toothed portion on its axial end face by sintering or forging.
In general, a medium- or small-size gear of this type is produced by a method in which powder of metal, such as iron, is pressed by a mold, and is sintered, and then the sintered product is again compressed by a die so as to correct its dimensions (This is called sizing). Similarly, a gear, formed by forging, is finished by sizing.
The sizing is effected by a method in which the sintered or forged workpiece is inserted into a lower punch of the die, and is pressed by an upper punch. When inserting the workpiece, the workpiece needs to be positioned so that a toothed portion formed on an axial end face of the workpiece mates with a toothed portion of the lower punch.
This positioning operation requires attention, and suffers from problems in that a die accident due to the improper positioning may occur, and that a dent may be formed in the toothed portion of the workpiece by a collision. Further, the required attention lowers the efficiency of the production, and hinders automation.